The present invention relates, in general, to a subtractor circuit and more particularly, to a high-speed voltage subtractor useful in an analog-to-digital converter.
Voltage substractors are useful in electronic circuits and particularly in analog-to-digital converters. In an analog to digital converter it is generally only necessary to determine the difference between two voltages which are somewhat close in magnitude to each other. It is much faster to switch current in a circuit than it is to switch voltage since most of the time capacitors or even parasitic capacitance will tend to slow down voltage switching. One such subtractor circuit is disclosed in U.S. Pat. No. 4,124,824 which issued Nov. 7, 1978 to Kreinick et al. It has been found that the voltage subtractor of the aforementioned patent can be simplified by the use of a precision high-speed operational amplifier.
Accordingly, it is an object of the present invention to provide a high-speed voltage subtractor which uses an operational amplifier.
Another object of the present invention is to provide a high-speed voltage subtractor having an operational amplifier and which uses current switching as opposed to voltage switching.